1. Field of the Invention
This invention relates to a tape cartridge having a high performance tape path therein. More particularly, the invention is a tape cartridge having a metal foil gas bearing surface therein and/or compliant members fitted within bearing edge recesses, and a method of manufacturing such a tape cartridge.
2. Description of the Related Art
Tape is a known medium for the storage of audio, video, and computer information. The information is typically written to and read from the tape magnetically and/or optically. Such tapes are available spooled on individual reels and in single or dual reel tape cassettes/cartridges. The tape in a single reel tape cartridge must be mechanically threaded through the tape path and spooled onto a take-up reel after insertion into a tape device/drive. The tape path for any type of tape cartridge and tape drive includes a tape head in close proximity to the tape and having one or more transducer elements for writing to and/or reading from the tape. The tape is driven past the tape head by a capstan, or by direct drive of the tape reels. As used herein, the terms "cassette" and "cartridge", and the terms "device" and "drive" are interchangeable.
For reliable operation of a tape drive, a tape cartridge and the tape therein must be capable of being accurately aligned to one or more tape heads in the tape drive. Known tape cartridges have shells (i.e. outer materials) manufactured from plastic or other materials which deform easily from mechanical and/or thermal stress. Such stresses may occur during the storage, manual handling, and automated handling of the tape cartridges, including the mounting and demounting of the tape cartridges in a tape drive. In addition, similar materials are used for the internal parts of known tape cartridges. Such materials make accurate alignment of the tape and tape heads difficult, and subject to alteration during aging and handling. Finally, known tape cartridges include various moving parts. For example, tape reels are known to be movable laterally (i.e. along the axis of rotation within a tape cartridge to permit them to be moved into and out of engagement with a tape reel brake. Such lateral movement further degrades the ability to accurately align the tape and tape heads. Thus, a heretofore unrecognized problem is the creation of a tape cartridge in which the tape therein can be accurately and repeatedly aligned with tape heads in a tape drive.
Another problem associated with tape drives and tape cartridges is that of pneumatic tape guiding. Pneumatic tape guides using air bearings to support the tape are known in various tape drives. Such tape guides are desirable for high performance tape paths. However, such tape guides use metal stock to create a precisely shaped and smoothly polished tape path. Such metal stock is expensive and must be machined or die-cast into the desired shape and contour. In addition, dual reel tape cartridges usually require tape guides in the cartridge. The use of such metal stock and complex machining increases the cost of tape cartridges, traditionally a low cost item used in large quantity. Gas bearing tape guides having a metal foil affixed to a plenum in a tape drive have been attempted, but have been unsuccessful because of the materials and manufacturing techniques employed. Thus, a heretofore unrecognized problem is the creation of a dual reel tape cartridge which includes pneumatic tape guiding for a high performance tape path while minimizing cost.
Another problem associated with tape drives and tape cartridges is that of tape edge guiding. Tape edge guiding is typically provided by locating compliant guides adjacent the bearing surface, which is slightly narrower than the tape. The tape thickness is minimized to permit the maximum amount of tape in a tape cartridge. As the tape thickness is reduced, the tape becomes more susceptible to tape vibrations resulting from the tape folding over the edge of the narrower bearing surface. Tape vibrations are reduced by providing full bearing support for the tape across its width (i.e. the tape is narrower than the supporting bearing surface). Compliant members are again located adjacent the bearing surface to maintain the tape thereover. When the tape temporarily wanders off of the bearing surface, and before the tape is guided back thereover, the edge of the tape is unsupported by the bearing surface. Such lack of support again renders the edge of very thin tapes susceptible to vibrations which can propagate along the tape and eventually disrupt the head-tape interface. Compliant guides fitted within recesses in thick bearing surfaces in a tape drive to provide additional tape edge support are known, but are not practical for use in a tape cartridge. Thus, a heretofore unrecognized problem is the elimination of tape vibration resulting from a lack of tape edge support during edge guiding.
Another problem associated with tape drives and tape cartridges is that of contamination. Dust, wear particles and other contaminants can cause signal dropout and the abrasion of moving parts and thus degrade performance of a tape drive and/or tape cartridge. The cleaning of tape drives and tape cartridges using various mechanical and chemical techniques is known. However, the high performance tape drives of the future will not be able to tolerate the levels of contamination found in current tape drives, before or after such cleaning.
Tape cartridges are particularly susceptible to contamination when removed from a tape drive. Dust, wear particles and other contaminants that enter the interior of a tape cartridge migrate throughout the cartridge and can be transferred to a tape drive when the tape cartridge is inserted therein. Some known tape cartridges include a tape access door to reduce such contamination. The access door is opened when the tape cartridge is inserted into a tape drive to permit mating of the tape head and the tape. The access door is closed when the tape cartridge is removed from the tape drive.
Unfortunately, tape cartridges are susceptible to contamination through other openings therein. One such opening permits access to a tape reel hub for proper seating of the tape cartridge in a tape drive and/or for mating a motor driven clutch or gear to the hub for rotatably driving the hub. The crutch face enters the tape cartridge opening and moves the hub laterally within the tape cartridge (i.e. depresses the hub away from the opening) to driveably mate with the hub. As previously mentioned, such movement of the hub degrades the ability to accurately align the tape and tape heads. In addition, the lateral movement of a tape hub may require a wider tape cartridge. Thus, a heretofore unrecognized problem is the creation of a tape cartridge which achieves the high performance demanded of future tape drives, including the aforementioned tape path characteristics, yet minimizes tape cartridge contamination through hub access openings.
Another problem associated with dual reel tape cartridges is that of tape tension. In such tape cartridges the tape is always threaded between the tape reels. The precise control of tape tension when a tape cartridge is mounted in a tape drive is well known. Such control includes the sensing and mechanical adjustment of tape tension by the tape drive. When a dual reel tape cartridge is removed from the tape drive, however, such control is no longer possible.
The tape tension varies as the tape moves therewithin during handling of the tape cartridge outside of the tape drive. When a dual reel tape cartridge is inserted into a tape drive the tape head is mated with the tape to press inwardly thereagainst. When the tape cartridge is removed from the tape drive, the absence of the tape head results in reduced tape tension between the tape reels (i.e. leaves slack in the tape). The slack can migrate through the tape path during handling of the tape cartridge outside of the tape drive, causing the tape to unravel from the reels and become susceptible to damage. In addition, if the tape tension increases during handling outside of the tape drive (i.e. is pulled taut straight between the tape reels or tape guides of the tape cartridge), subsequent insertion of the tape cartridge into a tape drive may result in stretching or other deformation of the tape by the tape head. Such deformation degrades performance of the tape drive and/or tape cartridge. Thus, a heretofore unrecognized problem is the creation of a tape cartridge which maintains constant tape tension during handling of the tape cartridge outside of a tape drive.